This is a new revision of the discovery server. Relevant changes and non-changes: - Protocol towards clients is unchanged. - Recommended large scale design is still to be deployed nehind nginx (I tested, and it's still a lot faster at terminating TLS). - Database backend is leveldb again, only. It scales enough, is easy to setup, and we don't need any backend to take care of. - Server supports replication. This is a simple TCP channel - protect it with a firewall when deploying over the internet. (We deploy this within the same datacenter, and with firewall.) Any incoming client announces are sent over the replication channel(s) to other peer discosrvs. Incoming replication changes are applied to the database as if they came from clients, but without the TLS/certificate overhead. - Metrics are exposed using the prometheus library, when enabled. - The database values and replication protocol is protobuf, because JSON was quite CPU intensive when I tried that and benchmarked it. - The "Retry-After" value for failed lookups gets slowly increased from a default of 120 seconds, by 5 seconds for each failed lookup, independently by each discosrv. This lowers the query load over time for clients that are never seen. The Retry-After maxes out at 3600 after a couple of weeks of this increase. The number of failed lookups is stored in the database, now and then (avoiding making each lookup a database put). All in all this means clients can be pointed towards a cluster using just multiple A / AAAA records to gain both load sharing and redundancy (if one is down, clients will talk to the remaining ones). GitHub-Pull-Request: https://github.com/syncthing/syncthing/pull/4648
193 lines
4.2 KiB
Go
193 lines
4.2 KiB
Go
package humanize
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/*
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Slightly adapted from the source to fit go-humanize.
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Author: https://github.com/gorhill
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Source: https://gist.github.com/gorhill/5285193
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*/
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import (
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"math"
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"strconv"
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)
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var (
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renderFloatPrecisionMultipliers = [...]float64{
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1,
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10,
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100,
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1000,
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10000,
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100000,
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1000000,
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10000000,
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100000000,
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1000000000,
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}
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renderFloatPrecisionRounders = [...]float64{
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0.5,
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0.05,
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0.005,
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0.0005,
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0.00005,
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0.000005,
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0.0000005,
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0.00000005,
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0.000000005,
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0.0000000005,
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}
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)
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// FormatFloat produces a formatted number as string based on the following user-specified criteria:
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// * thousands separator
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// * decimal separator
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// * decimal precision
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//
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// Usage: s := RenderFloat(format, n)
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// The format parameter tells how to render the number n.
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//
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// See examples: http://play.golang.org/p/LXc1Ddm1lJ
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//
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// Examples of format strings, given n = 12345.6789:
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// "#,###.##" => "12,345.67"
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// "#,###." => "12,345"
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// "#,###" => "12345,678"
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// "#\u202F###,##" => "12 345,68"
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// "#.###,###### => 12.345,678900
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// "" (aka default format) => 12,345.67
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//
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// The highest precision allowed is 9 digits after the decimal symbol.
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// There is also a version for integer number, FormatInteger(),
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// which is convenient for calls within template.
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func FormatFloat(format string, n float64) string {
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// Special cases:
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// NaN = "NaN"
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// +Inf = "+Infinity"
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// -Inf = "-Infinity"
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if math.IsNaN(n) {
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return "NaN"
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}
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if n > math.MaxFloat64 {
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return "Infinity"
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}
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if n < -math.MaxFloat64 {
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return "-Infinity"
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}
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// default format
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precision := 2
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decimalStr := "."
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thousandStr := ","
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positiveStr := ""
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negativeStr := "-"
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if len(format) > 0 {
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format := []rune(format)
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// If there is an explicit format directive,
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// then default values are these:
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precision = 9
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thousandStr = ""
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// collect indices of meaningful formatting directives
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formatIndx := []int{}
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for i, char := range format {
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if char != '#' && char != '0' {
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formatIndx = append(formatIndx, i)
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}
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}
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if len(formatIndx) > 0 {
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// Directive at index 0:
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// Must be a '+'
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// Raise an error if not the case
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// index: 0123456789
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// +0.000,000
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// +000,000.0
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// +0000.00
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// +0000
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if formatIndx[0] == 0 {
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if format[formatIndx[0]] != '+' {
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panic("RenderFloat(): invalid positive sign directive")
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}
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positiveStr = "+"
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formatIndx = formatIndx[1:]
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}
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// Two directives:
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// First is thousands separator
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// Raise an error if not followed by 3-digit
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// 0123456789
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// 0.000,000
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// 000,000.00
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if len(formatIndx) == 2 {
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if (formatIndx[1] - formatIndx[0]) != 4 {
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panic("RenderFloat(): thousands separator directive must be followed by 3 digit-specifiers")
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}
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thousandStr = string(format[formatIndx[0]])
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formatIndx = formatIndx[1:]
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}
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// One directive:
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// Directive is decimal separator
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// The number of digit-specifier following the separator indicates wanted precision
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// 0123456789
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// 0.00
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// 000,0000
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if len(formatIndx) == 1 {
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decimalStr = string(format[formatIndx[0]])
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precision = len(format) - formatIndx[0] - 1
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}
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}
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}
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// generate sign part
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var signStr string
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if n >= 0.000000001 {
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signStr = positiveStr
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} else if n <= -0.000000001 {
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signStr = negativeStr
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n = -n
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} else {
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signStr = ""
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n = 0.0
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}
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// split number into integer and fractional parts
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intf, fracf := math.Modf(n + renderFloatPrecisionRounders[precision])
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// generate integer part string
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intStr := strconv.FormatInt(int64(intf), 10)
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// add thousand separator if required
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if len(thousandStr) > 0 {
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for i := len(intStr); i > 3; {
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i -= 3
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intStr = intStr[:i] + thousandStr + intStr[i:]
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}
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}
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// no fractional part, we can leave now
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if precision == 0 {
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return signStr + intStr
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}
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// generate fractional part
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fracStr := strconv.Itoa(int(fracf * renderFloatPrecisionMultipliers[precision]))
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// may need padding
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if len(fracStr) < precision {
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fracStr = "000000000000000"[:precision-len(fracStr)] + fracStr
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}
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return signStr + intStr + decimalStr + fracStr
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}
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// FormatInteger produces a formatted number as string.
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// See FormatFloat.
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func FormatInteger(format string, n int) string {
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return FormatFloat(format, float64(n))
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}
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